Bioresource Technology 98 (2007) 2148–2153

Effect of adding insoluble solids from surimi washwater on the functional and mechanical properties of pacific

whiting grade A surimi

Jose A. Ramırez a,1, Gonzalo Velazquez a,1, Gerardo Lopez Echevarrıa a,1,J. Antonio Torres b,*

a Departamento de Tecnologıa de Alimentos, UAM-Reynosa-Aztlan, Universidad Autonoma de Tamaulipas, Apdo. Postal 1015,

Reynosa, Tamaulipas 88700, Mexicob Food Process Engineering Group, Oregon State University, Corvallis, OR 97331-6602, United States

Received 14 February 2006; received in revised form 18 August 2006; accepted 24 August 2006Available online 27 October 2006

Abstract

Surimi processors are seeking means to improve the utilization of seafood resources to increase productivity and also in response tothe strong public pressure on this industry to reduce the organic matter in processing water discharged into the environment. Insolublesolids (IS) can be recovered from surimi wash water (SWW) by centrifugation. The quality implications of adding 0 (control), 1%, 3%and 5% of solids (SWW-IS) into surimi paste and gels were evaluated by determining their mechanical properties, moisture retention andcolor. This study showed that adding 1% SWW-IS improved the mechanical properties of Pacific whiting surimi with a minimal effect oncolor. Higher additions resulted in quality deterioration in mechanical properties and color.� 2006 Published by Elsevier Ltd.

Keywords: Pacific whiting; Surimi wash water; Insoluble proteins; Mechanical properties; Color

1. Introduction

Seafood processing requires a large amount of freshwa-ter which is often discharged from the plant carrying pro-teins and oils (Carawan et al., 1986). The processing ofPacific whiting, Alaska Pollock, and shrimp in Oregon,Alaska, and Washington generates 20 million ton/year ofprocessing water (Park, 2000) which should be treatedbefore discharging it to the environment. In the PacificNorthwest, the most utilized fish species for surimi produc-tion are Pacific whiting and Alaska Pollock. Surimi pro-duction requires cleaning, mincing and washingoperations using typically about 5.7 L of water per kg ofraw fish with approximately 35% of this freshwater used

0960-8524/$ - see front matter � 2006 Published by Elsevier Ltd.

doi:10.1016/j.biortech.2006.08.024

* Corresponding author. Tel.: +1 541 737 4757; fax: +1 541 737 6174.E-mail address: J_Antonio.Torres@OregonState.edu (J.A. Torres).

1 PMB 374, 501 N. Bridge St., Hidalgo, TX 78557, United States.

for cleaning and mincing, and the remaining 65% for mincewashing operations (Huang et al., 1997). Washing elimi-nates sarcoplasmic proteins, blood, fat and nitrogenouscompounds but also removes small minced fish particles(Park and Morrissey, 2000; Morrissey et al., 2000). Surimiwash water (SWW) contains about 0.5–2.3% total proteincomposed mostly of sarcoplasmic proteins with smallamounts of the myofibrillar proteins myosin and actin(Lin and Park, 1996; Park and Morrissey, 2000; Morrisseyet al., 2000; Savant and Torres, 2003). Recovering proteinfrom SWW not only produces protein for food and feedbut also generates treated water for potential reuse in theseafood processing plant.

US government offices responsible for ensuring compli-ance with the requirements of the Federal Water PollutionControl Act such as the Office of Wastewater Manage-ment (OWM) and the Environmental Protection Agency(EPA) have not developed policies to discourage the high

J.A. Ramırez et al. / Bioresource Technology 98 (2007) 2148–2153 2149

consumption of freshwater by seafood processing plants.Also, local agencies providing utility services in coastal cit-ies do not discourage the excessive use of this scarceresource, e.g., by charging higher fees for industrial cus-tomers consuming larger freshwater volumes (Terebus,2002). However, surimi plants operating on-shore, are fac-ing strong environmental pressures on their operationsbecause several processing aspects have become a majorpublic concern. They include the poor utilization of fishresources, the large use of freshwater that threatens theavailability of this resource for other users, and the nega-tive impact on the environment as a result of dischargingprocessing water that has not been adequately treated(Carawan, 1991).

Many protein sources have been employed to improvethe mechanical properties of surimi gels. The most fre-quently used are egg white and whey protein concentrates;other sources such as leguminous extracts and porcineplasma protein have been proposed. These proteins areadded to inhibit the Modori phenomenon, i.e., the prote-olytic degradation of fish myosin when gels are incubatedat 60 �C, and to favor gel setting by the action of endog-enous and added transglutaminase enzymes (An et al.,1996; Garcıa-Carreno, 1996; Sanchez et al., 1998; Benja-kul et al., 2001). The objective of this work was to recoverinsoluble proteins from Pacific whiting SWW and assessthe impact on mechanical properties, moisture retentionand color when added to commercial Pacific whiting gradeA surimi.

2. Methods

2.1. Dry insoluble SWW solids

SWW obtained from Pacific whiting (Merluccius produc-

tus) processing was collected from a commercial plant(Pacific Surimi Joint Venture L.L.C., Warrenton, OR) atthe rotary stage used to remove solid fish waste from surimiprocessing water (Morrissey et al., 2000) and transportedrefrigerated to Corvallis, OR. The SWW collected in fourtrips to the processing plant, approximately 28 L each time,was centrifuged for 20 min at 3100 g (Model J-6B, Beck-man Coulter, Inc., Fullerton, CA) at 4 �C to recover insol-uble solids (SWW-IS) which were immediately frozen.Sorbitol (1%) was added as a cryoprotectant to preventlow-temperature damage to SWW proteins. The lots ofrecovered SWW-IS were frozen at �30 �C and thenfreeze-dried using a �60 �C condensing plate and no sam-ple heating to minimize damage to the functional proper-ties of proteins. The dehydrated SWW-IS was combinedinto a single sample and analyzed for moisture, protein,fat and carbohydrate content, according to official methods(AOAC, 1980). Composition data was previously reportedby Wibowo et al. (2005). Dried SWW-IS was then storedunder refrigeration (4 �C) until use in this study. The samematerial was used for a feed study previously reported(Wibowo et al., 2005).

2.2. Solubilized fish pastes and gels

Commercial grade A frozen Pacific whiting surimi par-tially thawed (4 �C) overnight was cut into small pieces tofacilitate mixing with SWW-IS. The moisture contentremoved by freeze-drying from SWW-IS was restored byadding distilled water (11.7 g water/g solids). Surimi pastesamples (500 g) were prepared in a 5.5 L capacity Hobartcutter (Model 84145, Troy, OH) by mixing for 4 min com-mercial surimi with rehydrated SWW-IS at 0 (control), 1%,3% and 5%. The final chopping temperature was main-tained below 15 �C and 2% salt was added to help solubi-lize myofibrillar proteins. The paste was stuffed intostainless steel tubes (internal diameter = 20.8 mm;length = 175 mm) previously sprayed with commercial veg-etable oil to prevent sticking. The tubes were capped beforeimmersion for 15 min in a water bath at 90 �C and thenimmediately placed for 30 min in a 4–5 �C water bath.Prior to testing, fish gels were removed from the tubesand stored overnight at 4 �C in polyethylene bags.

2.3. Expressible water

The expressible water content (EW) for each treatmentwas measured using the procedures described by Urestiet al. (2003) and implemented as follows. Triplicate sam-ples (3 ± 0.2 g) of solubilized fish paste or gel, placedbetween two layers of filter paper, were loaded at the bot-tom of 50 mL centrifuge tubes and centrifuged at 1000g for15 min at 4 �C. Immediately after centrifugation, the solu-bilized fish paste or gel samples were weighted and the EWwas calculated as follows:

EW ¼ W i � W f

W i

� 100

where Wi and Wf are the initial and final sample weight.

2.4. Color

Spectral reflectance of surimi paste and gels were deter-mined following the procedures described by Uresti et al.(2003) using a HunterLab MiniScan XE Plus spectrocolor-imeter (Model 45/0-L, Hunter Assoc., Reston, VA) cali-brated against black and white tiles. L*, a*, and b*

values, chroma (C* = [a*2 + b*2]1/2), and hue angle(H* = arc tan b*/a*) were calculated based on illuminantC and the 2� standard observer. Six samples were evaluatedat each SWW-IS concentration.

2.5. Back-extrusion of fish paste

A TA.XT2i Texture Analyzer (Stable Micro Systems,Vienna Court, UK) with a back extrusion rig (model A/BE, 40 mm inner diameter) was used to measure the forcerequired for the product to be extruded around a 35 mmpiston disc using the technique described by Uresti et al.(2003) and implemented as follows. Samples (30 g) stored

5

10

15

20

0 1 2 3 4 5Insoluble protein (%)

Exp

ress

ible

wat

er (

%)

aab ab

b

Fig. 1. Effect of insoluble protein concentration on the expressible waterof surimi paste. Mean values of six replicates. Bars show standarddeviation. (a–c) Different letters indicate significant difference (P 6 0.05)between treatments.

0

1

2

3

4

5

6

0 1 2 3 4 5Insoluble protein (%)

Firm

ness

(kg

)

0

10

20

30

40

Con

sist

ency

(m

m2 )

FirmnessConsistency

c

a

bcc

ba

bb

Fig. 2. Effect of insoluble protein concentration on the firmness andconsistency of surimi paste. Mean values of six replicates. Bars showstandard deviation. (a–c) Different letters indicate significant difference(P 6 0.05) between treatments.

2150 J.A. Ramırez et al. / Bioresource Technology 98 (2007) 2148–2153

at room temperature (26 �C) for 2 h before analysis wereintroduced into the cell avoiding air bubbles and extrudedat 1 mm/s to 80% of its initial height (17.5 mm ± 1.3 mm).The maximum force and the area under the curve weredefined as the firmness and consistency of the solubilizedpaste, respectively. Six samples were evaluated at eachSWW-IS concentration.

2.6. Mechanical properties of fish gels

Mechanical properties were measured using theTA-XT2i Texturometer (Stable Micro Systems, ViennaCourt, UK) and following the technique described byUresti et al. (2003). Cylindrical surimi gel samples (diame-ter = 20.8 mm, height = 25 mm) held in plastic containersto avoid dehydration, were equilibrated to room tempera-ture for 30 min before testing by Texture Profile Analysis(TPA). A 50 mm aluminum cylindrical probe (P/50) wasused to compress samples at 1 mm/s to 75% of their initialheight. The texturometer software (Texture Expert forWindows, Stable Micro Systems) was used to determinehardness, fracturability, springiness, cohesiveness andchewiness values.

Puncture test were performed compressing surimi gels(diameter = 20.8 mm, height = 25 mm) to 75% of initialheight using a compression speed of 1 mm/s and a sphericalprobe (diameter = 12.7 mm). Samples were placed on thebase of the texturometer, ensuring that the spherical probereached the sample at its center point. The breaking force(kg), deformation (mm) and gel strength (kg · mm) foreach treatment were measured. In both TPA and puncturetests, six samples were evaluated at each SWW-ISconcentration.

2.7. Statistical analysis

Statistical analysis was performed using Statgraphics 5.0(Bitstream Inc., Cambridge, MA). LSD’s multiple rangetests were used to determine significantly difference(P 6 0.05) among treatments.

3. Results and discussion

In this work the feasibility of using insoluble solids (IS)recovered from Pacific whiting surimi washing water(SWW) to improve mechanical and functional propertieswas studied. Pacific whiting SWW-IS solubilized by theaddition of 2% salt were added to grade A surimi. Theserecovered solids (SWW-IS) contained 9.6% moisture,13.7% ash, 14.5% fat, 61.4% protein and 0.8%carbohydrates.

3.1. Changes in surimi paste properties

3.1.1. Expressible waterExpressible water (EW), a property inversely associated

with the water holding capacity (WHC) of a food system,

varied from 15.8% to 12.7% (Fig. 1). Control surimi pastesshowed the highest EW value. Samples containing 3%SWW-IS showed a significantly lower EW value as com-pared with the control (P 6 0.05). This result suggests that3% SWW-IS increased the WHC of fish paste.

3.1.2. Backward extrusion of surimi paste

The firmness and consistency of the solubilized surimipaste containing SWW-IS was measured by backwardextrusion (Fig. 2). Backward extrusion has been reportedas useful in determining changes in firmness and consis-tency of fish paste induced by the addition of amidated,low-methoxyl pectins (Uresti et al., 2003). In this studyboth parameters decreased significantly (P 6 0.05) by theaddition of the insoluble proteins with firmness changingfrom 3.9 kg (control) to 3.3 kg in samples containing 5%SWW-IS while consistency decreased from 35.7 mm2 to27.7 mm2.

Uresti et al. (2003) reported that fish paste added withlow-methoxyl pectins showed a decrease in firmness andconsistency associated with a decrease in protein–waterinteractions with a consequent increase in protein–carbo-hydrate interactions. In this study adding the insoluble pro-

0

5

10

15

20

25

0 1 2 3Insoluble protein (%)

Exp

ress

ible

wat

er (

%)

0

5

10

15

20

25

4 5Insoluble protein (%)

bb

b

a

J.A. Ramırez et al. / Bioresource Technology 98 (2007) 2148–2153 2151

teins contained in SWW-IS induced a slight decrease infirmness and consistency associated with a slight increasein the water holding capacity of surimi paste. This resultsuggests that SWW-IS added to surimi competes with mus-cle protein for water, causing a decrease in firmness andconsistency of fish paste.The SWW-IS–water interactionseems to be associated with a decreasing in functional(WHC) and mechanical properties (TPA and puncture test)of surimi gels.

Fig. 3. Expressible water of surimi paste containing different concentra-tions of insoluble protein. Mean values of six replicates. Bars showstandard deviation. (a–c) Different letters indicate significant difference(P 6 0.05) between treatments.

3.1.3. Color

Surimi paste color attributes are shown in Table 1. Add-ing 1 to 5% SWW-IS induced small changes in the L* attri-bute, varying from 71.5 to 72.8. The a* value increasedsignificantly (P 6 0.05) only for the sample containing 5%SWW-IS reflecting a slight increase in redness as comparedto the control paste. The b* parameter increased signifi-cantly in all samples containing SWW-IS indicating anincrease in yellowness. The highest b* value was observedfor the sample containing 5% SWW-IS. Results obtainedindicate that adding SWW-IS induced a more reddishhue* (decreasing from 102.5 to 98.5) and higher chroma*

(increasing from 7.8 to 10.5). These results indicate thatalthough the surimi paste had a yellow-greenish hue (H*

value slightly higher than 90, corresponding to yellow),the surimi paste will be perceived as light grayish becauseof the low C* value and the relatively high L* value (70.7for control and 71.5–72.8 for samples containing SWW-IS). Although changes in H* and C* were small they maybe noticeable to consumers.

3.2. Changes in surimi gel properties

3.2.1. Expressible water

Control surimi gels showed an EW value of 12.2% whileadding SWW-IS increased the amount of expressible water(Fig. 3). Gels containing 1–5% SWW-IS showed an EWvalue varying from 18.5% to 21.4% indicating a loss inwater holding capacity of the gels. The decreasing inWHC in fish gel containing SWW-IS could be associatedwith a lower WHC of SWW-IS as compared to myofibrillar

Table 1Effect of insoluble protein concentration on color parameters of surimipaste

Protein (%) L* a* b* Chroma Hue

0 70.7a �1.7a 7.6a 7.8a 102.5a

(1.2) (0.03) (0.3) (0.3) (0.5)1 72.8b �1.6a,b 9.5b 9.6b 99.6b

(0.6) (0.04) (0.3) (0.3) (0.5)3 72.7b �1.6a,b 9.8b 9.9b 99.5b

(0.8) (0.06) (0.3) (0.3) (0.55 71.5a �1.5b 10.4c 10.5b 98.5b

(1.1) (0.12) (0.5) (0.5) (0.9)

(a–c) Different letters indicate differences between treatments (P < 0:05).Mean values of six replicates. Values in parentheses indicate the standarddeviations of the means.

proteins, a disruptive effect on the gel structure (mechanicalproperties) observed as a decrease in the amount ofentrapped water, or a combination of both factors.

3.2.2. Mechanical properties

TPA parameters of surimi gels were affected by SWW-IS(Figs. 4 and 5). Control surimi gels showed a hardnessvalue of 2.78 kg (Fig. 4) while the hardness of gels contain-ing 1% and 3% SWW-IS was not significantly different(P > 0.05) from the control; however, it decreased signifi-cantly at 5% SWW-IS. The fracturability value in samplescontaining 3% or 5% SWW-IS was significantly lower thanthe control gel (1.98 kg) (Fig. 4). Springiness and cohesive-ness values varied from 0.34 to 0.55 and 0.12 to 0.15,respectively, while chewiness were 0.10–0.19 kg (Fig. 5).Springiness and chewiness were not affected by adding 1–3% SWW-IS but at 5% a significant decrease in bothparameters was observed. Cohesiveness was very low incontrol gel (0.14 kg), changing only slightly with the addi-tion of SWW-IS in the concentration range tested.

Puncture test parameters as modified by the addition ofSWW-IS are shown in Fig. 6. Breaking force, deformationand gel strength values varied from 0.50 to 0.81 kg, 8.3 to10.6 mm and 4.2 to 8.3 kg mm, respectively. The breakingforce and gel strength of surimi gels containing 1% SWW-IS were significantly higher (P 6 0.05) than the control;

0

1

2

3

Hardness Fracturability

Forc

e (k

g)

0% 1% 3% 5%a a a

b

a a

bb

Fig. 4. Effect of insoluble protein concentration on the hardness andfracturability of surimi gels. Mean values of six replicates. Bars showstandard deviation. (a–c) Different letters indicate significant difference(P 6 0.05) between treatments.

0

0.2

0.4

0.6

Springiness Cohesiveness Chewiness

0% 1% 3% 5%a

a

ab

b

a a

b

a

a b ab

0

0.2

0.4

0.6

Coh

esiv

enes

s, S

prin

gine

ss

Che

win

ess

(kg)

Fig. 5. Effect of insoluble protein concentration on the spriginess,cohesiveness and chewiness of surimi gels. Mean values of six replicates.Bars shows standard deviation. (a–c) Different letters indicate significantdifference (P 6 0.05) between treatments.

0

2

4

6

8

10

0 1 2 3 4 5Insoluble protein (%)

Gel

str

engt

h (k

g m

m) 0

3

6

9

12

Def

orm

atio

n (m

m)

0

0.2

0.4

0.6

0.8

1

Bre

akin

g fo

rce

(kg)

c

b

c

a

abab

b

a

b

a

b

a

Fig. 6. Effect of insoluble protein concentration on the breaking force,deformation and gel strength of surimi gels. Mean values of six replicates.Bars show standard deviation. (a–c) Different letters indicate significantdifference (P 6 0.05) between treatments.

Table 2Effect of insoluble protein concentration in color parameters of surimi gels

Protein (%) L* a* b* Chroma Hue

0 74.7a �1.8a 6.3a 6.6a 106.1a

(1.2) (0.07) (0.1) (0.1) (0.4)1 77.1b �1.5b 7.8b 7.9b 100.9b

(0.5) (0.09) (0.3) (0.3) (1.0)3 76.3b �1.5b 7.6b 7.7b 100.8b

(1.1) (0.09) (0.2) (0.2) (0.9)5 74.2a �1.1c 8.9c 8.9c 96.92c

(1.3) (0.08) (0.3) (0.3) (0.7)

(a–c) Different letters indicate differences between treatments (P < 0:05).Mean values of six replicates. Values in parentheses indicate the standarddeviations of the means.

2152 J.A. Ramırez et al. / Bioresource Technology 98 (2007) 2148–2153

however a decreasing effect was observed at the higher con-centrations tested (3% and 5%).

3.2.3. Color

Surimi gel color attributes are shown in Table 2. Controlsurimi gels showed L*, C* and H* values of 74.7, 6.8 and106, respectively. These results indicate that surimi gelshad a yellow-greenish hue. However because of the lowchroma value and the relatively high L* value, surimi gelshad a light greyish appearance. Samples containing 1 to3% SWW-IS showed slightly higher L* values (P 6 0.05)than the control and the sample containing 5% SWW-IS(Table 2). The addition of SWW-IS increased the a* param-eter significantly reflecting a slight increase in redness. Theb* parameter increased from 6.6 in control gels to 8.9 ingels containing 5% SWW-IS, indicating an increase in yel-

lowness. Finally, the addition of these recovered solidsdecreased the hue value indicating a slight increase in yel-lowness, and consequently an increase in the chroma valueindicating that fish gels had a slightly more intense color.Although the addition of SWW-IS to commercial gradeA surimi affected its color attributes, surimi gels remainedin the greyish zone with changes in color that are not likelyto be perceived by most consumers.

4. Conclusions

The incorporation of SWW-IS to commercial surimiincreased the WHC of the paste prepared with 2% saltadded to facilitate protein solubilization. The same solidsaffected negatively the WHC of surimi gels while 1%SWW-IS increased some of the mechanical properties ofsurimi gels, but decreased the same properties when addedat 3% or 5%. These results suggest that when added at 1%,SWW-IS absorbs water molecules allowing a higher num-ber of protein–protein interactions, yielding an improvedstructure system as reflected in higher values for mechani-cal properties and low WHC. However, adding 3–5% ofSWW-IS decreased the values for the mechanical proper-ties and the WHC of the gel samples, suggesting that thehigher concentrations of SWW-IS affected the formationof the three dimensional network that gives its structureto fish gels.

Insoluble solids (SWW-IS) recovered from surimi washwater and added at 1% to Pacific whiting surimi gels,showed no adverse effect on their hardness and fracturabil-ity while increasing the values for breaking force and gelstrength parameters (puncture test). These positive changesand the small effect on color indicate that it is feasible touse SWW-IS while improving Pacific whiting surimi gels.

Acknowledgements

This work was supported by Grant no. NA 16RG 1039(Project no. R/SF-29) from the National Oceanic andAtmospheric Administration to the Sea Grant College Pro-gram at Oregon State University, and appropriations madeby the Oregon State Legislature.

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